1. Field of the Invention
Aspects of the present invention relate to a barrier rib-forming composition and to a plasma display panel including a barrier rib formed from the barrier rib-forming composition. More particularly, aspects of the present invention relate to a barrier rib-forming composition that resists an exposure sensitivity decrease caused by exposure to oxygen and thereby allows a high-sensitive, high resolution, and high-definition barrier rib to be formed in a process that requires only a single exposing.
2. Description of the Related Art
A plasma display panel (PDP) is a display device that forms an image by exciting a phosphor with vacuum ultraviolet (VUV) rays generated by gas discharge in discharge cells. Since a plasma display panel is capable of forming a large, high-resolution screen, thin plasma display devices have become popular. Recently, a reflective AC driving panel has been used for the plasma display panel, which includes a rear substrate formed with a phosphor layer on an interior portion between barrier ribs. A typical PDP has a structure as follows: On a rear substrate, address electrodes are disposed in one direction and a dielectric layer is disposed on the address electrodes. Barrier ribs are formed on the dielectric layer in a striped pattern. Red (R), green (G), and blue (B) phosphor layers are positioned on the discharge cells between the barrier ribs. On one surface of a front substrate facing the rear substrate, display electrodes are formed in a crossing direction to that of the address electrodes, wherein a display electrode is composed of a pair of transparent electrodes and a bus electrode. A dielectric layer and a protection layer are formed on the front substrate, and cover the display electrodes. A discharge cell is formed on the cross-section of the address electrodes of the rear substrate and the display electrodes of the front substrate.
The barrier ribs of the plasma display panel maintain a discharge space and prevent electro-optical cross-talk among discharge cells. Barrier ribs may be formed by forming an address electrode and a dielectric layer on a rear substrate of the plasma display panel and subjecting the deposited layer to sandblast, etching, or photolithography. Regarding photolithography, U.S. Pat. No. 6,197,480 discloses a method of fabricating a barrier rib can with a single exposure including: minimizing the refractive index difference of between a glass frit and a vehicle; and minimizing the photo scattering and reflectivity of irradiated light on the interface of the glass frit and the vehicle upon exposing the light. Similarly, U.S. Pat. No. 6,117,614 discloses a method of forming a barrier rib using a glass frit and a vehicle and in which the refractive index difference between the glass frit and the vehicle is minimized, as in U.S. Pat. No. 6,197,480. The vehicle includes a photoacid generator to promote a chemically amplified cross-linking reaction. However, although the photolithography methods disclosed in these patents have merits in the simple process compared to sandblasting and etching and in providing a high resolution barrier rib, they cause the following problems:
In the methods described in the above patents, it is impossible to add powders such as titania, alumina, silica, zirconia, yttria, magnesia, zinc oxide, or tin oxide which are used for maintaining the shape of the barrier ribs and increasing the reflectivity of the barrier ribs during baking processes in the sand blasting or etching methods. Because such powders have either a very high or a very low refractive index (for example, silica has a very low refractive index), it is impossible to minimize the refractive index difference between such powders and the vehicle. Further, these powders inhibit the transmission of irradiated ultraviolet such that the barrier ribs can not be formed by a single exposure. Solutions for increasing the reflective index of the barrier ribs have been suggested in Japanese Laid-open Publication No. 2004-318116. According to this publication, the reflectivity of barrier ribs can be increased by adding 5 to 80 nm particles such as titania, alumina, silica, zirconia, yttria, magnesia, zinc oxide, manganese oxide, iron oxide, tin oxide, copper oxide, lead oxide and so on. The addition of such particles increases the reflective index of the vehicle is increased and reduces the scattering or reflecting of the irradiated light during photolithography. Thereby, it is not necessary to add a glass frit having the low refractive index and a vehicle having a high refractive index. However, the method described in Japanese Laid-open Publication No. 2004-318116 has the disadvantage that when a paste is prepared by combining 5 to 80 nm particulates with a photosensitive organic component, the particulates tend to not be dispersed in the paste in the form of single particles, but rather become agglomerated. As the result, the agglomerated particles inhibit ultraviolet light from being transmitted through the material during formation of the barrier ribs and therefore, the barrier ribs cannot be formed in a single exposure.